Nickel-beryllium alloy



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I NICKEL-BERYLLIUM ALLOY Filed Dec. 21, 1959' 3 Sheets-Sheet l fiveiztdrCar Lo Adcuno Zi July 14, 1942. c. ADAMOLI 2,289,566

NICKEL-BERYLLIUM ALLOY Filed Dec. 21, 1959 3 Sheets-Sheet 2 Im'c' mo'csou-c coo-c more "00': name NMD A/Iag o 4 a .12 16 2o :4 2a 32 36 71.

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nIqKEL-BERYLLI ALLOY.

Filed Dec. 21}1939 I 3 Sheets-Sheet 3 N M Alloy o 4 a 1: rs :0 u 2a :2uh.

. n 5 lid enter 8- Carl 0 Adamo 22 Patented July 14, 1942NICKEL-BEBYLLIUM ALLOY Carlo Adamoli, Milan, Italy, assignor to PerosaCorporation, Wilmington, Del., a corporation of Delaware ApplicationDecember 21, 1939, Serial No. 310,387

- In Italy June 30, 1937 4 Claims.

The present application relates to a method for improvingnickel-beryllium alloys and is a continuation-in-part of my priorapplications Serial No. 172,871 filed on November 5, 1937, and SerialNo. 226,290 filed on August 23, 1938.

It is well known that from the technological point of view a metallicalloy is the more appreciated the more its structure is homogeneous andthe higher its physico-chemical characteristics such as hardness,mechanical tensile strength, elasticity, resistance to corrosion and thelike are.

In the course of the last years various berylhum-nickel alloys have beenproposed, but for none of them the necessity oi insuring a practicallyhomogeneous structure with the maximum oi. the above-mentionedphysico-chemical characteristics on a commercial scale has been takeninto account. Nor in the methods of thermal treatment which have alsobeen proposed for these Ni-Be alloys has the great importance of aperfectly homogeneous structure been taken into account. It resultstherefrom that with the present alloys inconveniences are frequentlyencountered which are due to the unavoidable separations or to theheterogeneousnesses which are not absorbed in a perfect manner at themoment of the solidification of the alloy. The resulting solid solutionshows interpositions between a grain and the other, namely small layersor small grains of a distinct constituent, and whatever may be made,either when the heating before quenching is protracted or when oneattempts to increase the temperature of the said heating (a thing whichis extremely dangerous), one does not succeed in causing the saidheterogeneous interpositions between a grain and the other to disappear.The scission of the supersaturated solid solution will take place,according to the known principle of Le Chatelier, certainly preferablyin the places where such localized heterogeneousnesses exist and thehardening constituent will form in excessive dimensions in theseintergranular spaces. Thus, one will have a hardened alloy, but an alloyin which the individual grains are not well bound together; accordingly,the alloy even then when it shows some mechanical characteristic ofinterest will not meet the optimum characteristic conditions, nor willit show a practically homogeneous structure. Such a structure may becompared with a masonry structure containing blocks having a resistanceattaining 1,000 kilogs. per square decimetre, but bound together by amortar the resistance of which does not exceed 200 kilogs.

per square decimeter. The individual blocks have a good resistance, butthe whole is structurally weak.

Now, after long studies which have been made with respect to the betterconditions of formation and scission of the-fundamental solid solutionof the Be-Ni alloys, I have succeeded not only in precising thephenomenon under a novel point 01 view, but also in discovering a noveland rational method for improving the physicochemico-mechanicalproperties of the Be-Ni alloys.

It may be said first, in orderto avoid any misunderstanding, that theexposed idea of homogeneous structure must not be considered in anabsolute but in a practical manner. The homogeneity which is admitted asbeing the practical one is that which can be deducted from the largestmicroscopical enlargements for the time being (500 to 1000 diameters).It is said that an alloy is practically homogeneous when, seen undersuch enlargementait dnes not show any structural heterogeneousness.

I have iound that the phenomenon of melioration of the nickel-berylliumalloys must not be considered exclusively as being due to thereprecipitatlon oi the hardening constituent but, already from thebeginning, to a diflusion of the beryllium atoms into the elemental cellof the nickel and to the subsequent formation of elemental particles ofthe hardening constituent Ni-Be. The dimensions at these groups increasein such a. manner that greater and greater stresses are exerted upon thereticle oi the solid solution of nickel up to a limit which can not beexceeded without the expulsion of the said crystalline groups out of therectile oi the solid solution taking place, and it is in this mannerthat the ire-precipitation takes place. In cor respcndence with thereality of the phenomena one has in the first phase an increase of theresistance to deformation and, parallelly to this, an increase of theelectric resistance and in the second phase a concomitant diminution ofthe electric resistance and of the mechanical strength. I do not intendto give more details which would not be in their place here, but I shalladd that, always guided by this analogy, i have admitted that thephenomenon oi the badly bound hardening constituents is due to the tactthat the reticular surface arrangement is much more altered than theinternal arrangement}; what amounts to admitting the presence of fineheterogeneous interpositions between the hardening constituents.

shown in Figure 1 of the ftity varying from 0.3 to about 1remainderbeing reducing the heterogeneousness of the interpositionsbetween the hardening constituents by promoting at the moment of thesolidification of the alloy their distribution and their solubilizationin the granular mass in a perfect manner. It is well known, indeed, thatthe cohesion force between metals and their saturated solution is thehigher the smaller the breaks of continuity between the crystals are, asresults from the following equation:

log

where 6 is the cohesion force, A the density and N the molecular weightof the solid body, S the normal solubility and Sw the solubility of theparticles the radius of which is 1'.

As regards the substance which is introduced into the alloy assolubilizing and homogenizing substance, it is advisable not to losesight of the fact that its specific action consists in annihilating orreducing in every way the surface deformations of the hardeningconstituents; the possibility for this action to appear is limited bythe quantity of additional substance which is introduced into thealloy'and which is always in small proportions. If the said quantityofintroduced substance were increased above a certain maximum, theaction would be altered in an essential manner; then hardening bodiesare formed which are distinctfrom the Ni-Be constituents and which, ontheir side, show the same inconveniences which are due to fineheterogeneous interpositions. The method of improvement does not attainto its purpose and alloys are obtained which are always inferior to theternary alloy which is described later on and which contains the thirdelement in the reduced proportions.

' For instance, if, according to the present invention, molybdenum isintroduced as solubilizing and homogenizing substance intonickelberyllium alloys, the ternary alloys Ni-Be-Mo for which themaximum physico-mechanical characteristics are obtained are those whichare indicated by the hachured part A of the diagram accompanyingdrawings and which relates to the Ni-Be-Mo system. It may beseen thatthe said alloys are those which for a' beryllium content varyingapproximately from. 1.4 to 1.7% contain molybdenum in a quantheremainder being substantially all nickel.

This action indicated for molybdenum. for

I beryllium alloys with a nickel basis has alsobeen vverified for thefollowing; substances which are diffusing,

'solubilizing' and homogenizing substances, i. e. tungsten, tantalum,chromium and zirconium. The followingf a're, only by way of example; thelimit proportions between which it, is advisable tointroduceithose'difierent substancesfinto the nickehberyllium alloysgenerally containing from 1 .4 t0"1. '7 '%i0f beryllium (thesubstantially, all nickel), in

.order to obtain the characteristic results of the present invention.

The so obtained alloys are subjected to a thermal treatment whichpreferably comprises heating to a temperature of 1000 to 1020" C. during30 to 45 minutes followed by a rapid cooling, for instance in water, andthen annealing at a temperature of about 485 C. to 500 C. during 6 tos15 hours to produce the re-precipitation of the hardening constituentdiffused in the basic metal, 1. e. the nickel, this complete treatmentbeing repeated if desired.

The alloys according to the present invention afford a considerabletechnical progress in the manufacture of springs, needles and all otherobjects or articles which especially necessitate a maximum of elasticityeven under very high mechanical stresses with a great hardness and alsoa greatly reduced oxidisability and a considerable facility formanufacture without any appreciable oxidation.

Alloys are especially obtained which possess a very high mechanicalstrength either as castings or as machinedpieces. These alloys possess avery great hardness and a very low consumption through wear and can thusbe used, among other things for ball or roller bearings, supports,springs as, for instance, laminated springs, and the like. v

The alloys according to the present invention, for instance theNi-Be-Mo, possess extremely high mechanical and electrical propertiesand take a good temper after heating at a temperature considerably lowerthan that required for the usual beryllium alloys, which has theadvantage of lessening and practically removing the risk of approachingthe fusion or disintegration temperature of the alloy. The solubilizingand homogenizing metal has the effect in this respect of lowering thetemperature which is necessary for the intersolubilisation of theconstituents of the alloy.

Berryllium alloys-as for instance nickelberyllium alloyshave alreadybeen manufactured and used for the manufacture of springs, needles orother very fine objects, but it has not been possible, on account of thedelicacy of these articles, to avoid the risk of causing burning of thealloy during the heating before quenching. In the same waynickel-beryllium alloys have been manufactured with the addition, in ahigh proportion, of another metal such as titanium, but the berylliumand titanium contents were very considerable and on account of this factthese alloys were very costly and very oxidisable and also brittle.Titanium, being in fact, in all the known alloys, used as a partialreplacement of beryllium, is always in excess of the quantity which isnecessary for the use hereunder consideration, and the excess oftitanium has a have been shown to possess a Brinell hardness of nearly500 with an annealing about 500 C. while the known alloys of Ni-Be showat most a Brinell hardness of about 400 with an annealing at 550 C.

Apart from the basis metal, beryllium and the solubilizing metal, thesealloys may contain, in addition, various elements in a very smallproportion; it is more particularly possible to add iron in a proportionwhich, in every case, is

smaller than 4% in order to give the alloy a very high fluidity incasting. It is only in the case of conducting alloys that it ispreferable to retrain from adding iron.

The alloys according to the invention, for instance the alloys Ni-Be-Mo,likewise display very greatly improved qualities and even moreparticularly for the conducting alloys a greatly improvedelectricaLconductivity when they have been subjected to physicaltreatments such as those mentioned above, for example thermal treatmentsof quenching and annealing, which secure their perfect homogeneity.

In the accompanying drawings various diagrams corresponding tocharacteristics of alloys 4 made according to the invention are given.

In these drawings:

Figure 2 is a diagram of the hardness curve of two Ni-Be-Mo alloys as afunction of the temperature to which the alloys are heated beforequenching. g

Figures 3 and 4 are diagrams of hardness curves for each of the twoalloys respectively,

v after quenching and annealing at the temperatures indicated on thecurves, they illustrate thus the variation of the hardness with varyingduration of annealing at specified temperatures.

Figure 5 is a diagram of curves showing the tensile strength (R) andelongation (A%) of an alloy according to the invention after quenchingand annealing, at the temperatures specified on the curves, illustratingthe variations of the tensile strength and elongation with varyingduration of annealing at specified temperatures.

The mean curves for Brinell hardness shown in Figure 2 correspond to thetwo following allows:

Normal nickel-beryllium-molybdenum alloy (referred to in the diagram bythe abbreviation N. M.) i

Be: between 1.4 and 1.6%.

Mo: between 0.3 and 0.5%.

Ni: the remainder.

Hard nickel-beryllium-molybdenum alloy (referred to in the diagram bythe abbreviation "N. M. D.) r

Be: between 1.4 and 1.7%. Mo: between 0.3 and 0.5%. N1: the remainder.

The mean curves of hardness in Figures 2 and 3 apply respectively to thetwo alloys above with nickel as base; referred to by the abbreviationsN. M. D. and N. M.. These curves give the variations in the hardnessafter annealing for different temperatures, as a function of theduration of annealing shown in hours H (abscissae).

Figure 4 relates solely to the alloy N. M.. The three curves in thinlines marked A" illustrate the variations in percentage e1ongation A%for varying periods of annealing at the annealing temperatures marked onthe curves. The five curves in heavy lines marked R show the variationsin tensile strength R in hgs. per mm. with varying periods of annealingat the temperatures shown on the curves.

What I claim is:

1. A process for improving the physico-mechanical properties of alloysof beryllium with nickel consisting in introducing into nickelberylliumalloys containing beryllium in the proportion of about 1.4 to 1.7%, as ametallic substance acting as a diffusing, solubilizing and homogenizingagent for beryllium, molybdenum in a proportion from 0.3 u to 1%, thebalance being substantially all nickel, heating the alloys soconstituted at a temperature of about 1000 to 1020 C., for 30 to 45minutes, then cooling the same rapidly and subjecting them to anannealing treatment producing the reprecipitation of the hardeningconstituent diffused in the alloys.

2. A process for improving the physico-mechanical properties of alloysof beryllium with nickel consisting in introducing into nickel berylliumalloys containing beryllium in the proportion of about 1.4 to 1.7%, as ametallic substance acting as a diffusing, solubilizing and homogenizingagent for beryllium, molybdenum in a proportion from 0.3 up to 1%, thebalance being substantially all nickel, heating the alloys soconstituted at a temperature of about 1000 to 1020' 0., for 30 to 45minutes, then cooling the same rapidly and subjecting them to anannealing treatment at a temperature of about 485 to 500 C. for six tofifteen hours.

3. A nickel-beryllium alloy containing beryllium in the proportion ofabout 1.4 to 1.7% and as a metallic substance acting as a diifusing,solubilizing and homogenizing agent for' beryllium, molybdenum in aproportion from 0.3 up to 1%, the balance being substantially allnickel.

4. A nickel-beryllium alloy containing beryllium in the proportionofabout 1.4 to 1.7% and as a metallic substance acting as a difiusing.solubilizing and homogenizing agent for beryllium, molybdenum in aproportion from about 0.3 up to 1%, the balance being substantially allnickel, the said alloy having been hardened by heating the alloy to atemperature of about 1000 to 1020 C., for 30 to 45 minutes, then coolingthe same rapidly and subjecting it to an annealing treatment at atemperature of about 485 to 500 C. for six to fifteen hours.

CARLO ADAMOLI.

